In the class of hearing aids generally referred to as implantable hearing instruments, some or all of various hearing augmentation componentry is positioned subcutaneously on, within or proximate to a patient's skull, typically at locations proximate the mastoid process. In this regard, implantable hearing instruments may be generally divided into two sub-classes, namely semi-implantable and fully implantable. In a semi-implantable hearing instrument, one or more components such as a microphone, signal processor, and transmitter may be externally located to receive, process, and inductively transmit an audio signal to implanted components such as a transducer. In a fully implantable hearing instrument, typically all of the components, e.g., the microphone, signal processor, and auditory stimulator, are located subcutaneously. In either arrangement, an implantable auditory stimulator device is utilized to stimulate a component of the patient's auditory system (e.g., tympanic membrane, ossicles and/or cochlea).
By way of example, one type of implantable transducer includes an electromechanical transducer having a magnetic coil that drives a vibratory actuator. The actuator is positioned to interface with and stimulate the ossicular chain of the patient via physical engagement. (See e.g., U.S. Pat. No. 5,702,342). In this regard, one or more bones of the ossicular chain are made to mechanically vibrate causing stimulation of the cochlea through its natural input, the so-called oval window.
As may be appreciated, hearing instruments that propose utilizing an implanted microphone, which include a diaphragm that will be covered by patient tissue, require that the microphone be positioned at a location that facilitates the transcutaneous receipt of ambient acoustic signals. For such purposes, an implantable microphone may be positioned (e.g., in a surgical procedure) between a patient's skull and skin, at a location rearward and upward of a patient's ear (e.g., in the mastoid region).